This invention relates to micromachined electrofluidic modules, their connection to a separate part or fixture, and their use in a multiplexing system.
Heretofore, there have been various and sundry assemblies of electronic and fluidic components. Such assemblies have, to one degree or another, attempted to obtain cooperation between the electronic and/or fluidic components in order to provide electrofluidic characteristics. Components have been assembled within a housing or in modular form. Such modular assemblies usually have an internal solenoid, electrical coil, electrothermal member, or an electrically responsive sensor such as used in a transducer, and have at least one fluidic passageway therein. Electrofluidic valves usually have both a fluidic inlet and a fluidic outlet, usually connected by fluidic hoses or pipes and have electrical leads attached thereto for connection to a control circuit. Solenoid controlled fluidic valves are usually quite large, although miniature solenoid valves are available, as will be described hereinafter. Also, as will be described hereinafter, there has been limited use of newer micromachined valves which are much smaller in size and use a movable member therein to modulate fluidic flow therethrough. While small micromachined valves are available, they are not effectively packaged to take advantage of their size where a large number of valves are needed, as in a complex fluidic system such as a fluidic multiplexing system.
Solenoid valves suffer a number of shortcomings when used in some applications where size, heat, weight, and noise of operation are important, such as in a dialysis system wherein over twenty solenoid valves have been used. Such dialysis systems are disclosed in U.S. Pat. No. 5,324,422, entitled "User Interface for Automated Peritoneal Dialysis Systems," issued to Colleran, et al., and assigned to Baxter International Inc.; and U.S. Pat. No. 5,350,357, entitled "Peritoneal Dialysis Systems Employing a Liquid Distribution and Pumping Cassette that Emulates Gravity Flow", issued to Kamen, et al., and assigned to Deka Products Limited Partnership. The pneumatic pressure distribution module in the Colleran/Kamen patents (see FIG. 9) has over 20 solenoid valves in two lines, with fluidic tubes extending between the inlet/outlets of the valves and the piston body.
While the pneumatic pressure distribution module disclosed in Colleran/Kamen serves its intended purpose of providing pneumatic actuating signals for the liquid valves, the module has several practical drawbacks. The module is relatively large and heavy, having an approximate size of twelve inches by four inches by two inches, and having a weight of approximately five pounds. The module includes over twenty solenoid actuated electromechanical valves, many of which are 3-way valves, requiring significant electricity and generating heat and substantial noise. The noise problems are particularly egregious, requiring a sound enclosure and remote mounting of the valves in a separate housing. The size of the Colleran module also resulted in mounting remotely from the piston element. The remote mounting causes a lag in the pneumatic actuating signals and liquid valve response time, and adding to the cost, size, and complexity of the overall system. A large number of lines and plumbing connections have to be made at the module and at the piston, which add to size, volume and complexity of the dialysis equipment. Thus, the shortcomings of the distribution module include the cost, size, weight, noise, heat, and power requirements. The shortcomings are accentuated by the fact that Colleran/Kamen systems are intended for home treatment of kidney dialysis patients, generally while the patient sleeps.
It was recognized that, while maintaining patient safety, it further would be desirable to reduce the size and cost of the pneumatic distribution module used with the peritoneal treatment apparatus. Unfortunately, components used in other applications often were found to be inadequate to meet these goals, particularly when used in peritoneal and other renal or medical treatment apparatus of the type discussed above.
In addition, the peritoneal treatment systems of the type shown in Colleran et al. may be relatively noisy due to the fact that the pneumatic valves are being actuated throughout the night while the patient is trying to sleep as he or she is connected to the peritoneal treatment system. Simple miniaturization of the valves, while continuing to use solenoidal valves, would not completely overcome the existing drawbacks as the relative volume of the manifolding with respect to the valves connected thereto would remain relatively large and, thus, the desired size and cost savings would not be achieved.
It was recognized that a distribution module might be made by trying to substitute for the larger solenoid valves, smaller miniaturized, solenoid valves of the type, for instance, available from SMC and identified by Model No. NVJ124A. Each of these three-way mini-valves is about an inch long, three-eighths (3/8) inch wide and three-quarters (3/4) inch high. Very small tubular solenoid actuated valves are available from the Lee Company and identified by Serial No. LHDX0500700AA. Four to ten of the Lee three-way valves have been configured in manifolding systems on a plastic manifold block having a pair of primary inlets and a number of outlets equal to the number of valves. Unfortunately, however, very significant dimensional savings cannot be achieved with solenoidal valves due to the fact that solenoidal valves often draw a significant amount of electric current when actuated, generating waste heat which must be dissipated.
The prior art is replete with various and sundry electrofluidic circuits having electrical circuits, electromechanical valves, and fluidic manifolds. See, e.g., U.S. Pat. No. 4,095,863 to Hardin, entitled "Manifold Means and System for Electrical and/or Pneumatic Control Devices and Method"; U.S. Pat. No. 4,165,139 to Asbill III, entitled "Manifolding Means and System for Electrical and/or Pneumatic Control Devices and Method"; U.S. Pat. No. 3,547,139 to Van Berkum, entitled "Fluid Logic Pack"; U.S. Pat. No. 3,646,963 to Klee, entitled "Duct System for Fluid Pressure Medium Operated Regulating, Control and Measuring Apparatus"; and U.S. Pat. No. 4,549,248 to Stoll, entitled "Electrofluidic Circuit Board Assembly with Fluid Ducts and Electrical Connections". Each of the aforementioned references suffers certain drawbacks in their large size, heavy weight, and application-specific designs.
In recent years, it has become known in the art that micromachined valves, for instance, of the type disclosed in U.S. Pat. No. 5,069,419 to Jerman, are available commercially. Such valves have each been enclosed in individual packages with a single inlet and a single outlet for control of small amounts of fluid flow therethrough. The silicon micromachined valves are quite small, being embodied on square or rectangular silicon dies which may be measured into fractions of an inch and are only a few thousandths thick. However, the housings within which the micromachined valves have been enclosed are orders of magnitude larger than the valves themselves and are relatively bulky in comparison to the micromachined valve itself. In addition, micromachined valves are relatively fragile as compared to solenoidal valves. However, they do not draw large amounts of current as they are usually activated by the heating caused by electric current flowing through a doped region, causing differential expansion of layers in the micromachined valve effecting movement between a boss and a valve seat. Such valves are available, for instance, from IC Sensors Model No. ICS 4425. Similar valves are available from Redwood Systems and are sold under the trademark "FLUISTOR.TM.". The valves are packaged one per package with the valves specifically being mounted within a TO8 can having a single gas inlet and a single gas outlet. The TO8 can may be mounted projecting upwardly from a printed circuit board on which electrical traces may be formed to provide an electrical connection to the valve so that electrical signals may be fed to the valve to control its state, and thereby to control fluid flow through the valve.
Similarly, the shape memory alloy film actuated microvalve disclosed in Johnson U.S. Pat. No. 5,325,880, discloses the packaging of a microvalve in a T08 can, see FIG. 2. U.S. Pat. No. 5,329,965 to Gordon, entitled "Hybrid Valving System for Varying Fluid Flow Rate", discloses a schematic diagram of a fluid flow valving system incorporating a Fluistor.TM. microvalve and disclosing as an alternative, a gas microvalve Model No. 4425 sold by IC Sensors. The Gordon '965 patent apparently requires the use of a separate inlet tube and outlet tube as well as a circuit board.
In addition to Jerman, Pat. No. 5,069,419, other micromachined devices are disclosed in U.S. Pat. No. 5,325,880 to Johnson, et al., entitled "Shape Memory Alloy Film Actuated Microvalve"; U.S. Pat. No. 5,180,623 to Ohnstein, entitled "Electronic Microvalve Apparatus and Fabrication"; U.S. Pat. No. 4,821,997 to Zdeblick, entitled "Integrated, Microminiature Electric-to-Fluidic Valve and Pressure/Flow Regulator"; and U.S. Pat. No. 5,322,258 to Bosch, et al., entitled "Micromechanical Actuator."
It is to be understood that the term micromachined devices as used herein is generic not only to micromachined electrofluidic valves but also to other micromachined devices such as electrofluidic pressure transducers. An example of a commercially available micromachined pressure transducer is Model Number FPM-15PG, available from Fujikura of Japan. The pressure transducer body has a single fluidic input line for a single transducer therein, as well as electrical connections for the single transducer for plugging into appropriate electrical devices. The aforementioned Fujikura pressure transducer has been used commercially with the pressure distribution module disclosed in the Colleran '422 patent, see reference numeral 178, FIG. 18.
Two other patents, the Bosch '258 patent and the Zdeblick '997 patent, disclose arrays of microvalves, see Bosch, FIG. 6, and Zdeblick, FIG. 66. However, neither Bosch nor Zdeblick disclose the electrical circuitry and fluidic connections needed for handling the fluidic inputs and outputs for the valves in the arrays.
The use of electrostatically actuated microvalves, which may use a shape memory film relying on the martensitic transformation phenomenon, in a matrix-like arrangement is disclosed in U.S. Pat. No. 5,284,179 to Shikida, et al., entitled "Valve and Semiconductor Fabricating Equipment Using the Same". The Shikida '179 patent discloses multiple inlets and multiple outlets, with multiple shape memory microvalves which may be placed in a single layer within a fluidic manifold or may be placed at multiple levels within a more complex fluidic manifold, see FIGS. 7b, 8, and 18. The Shikida patent suffers from drawbacks in that it appears to be a complicated and difficult system to build, and the microvalves are difficult or impossible to access for repair or replacement. Moreover, the Shikida disclosure is for an application-specific design, and is not a package or module of electrical and fluidic components having general applicability. That is, unlike individual valves which may be attached or detached if one of them becomes defective, the entire matrix must be discarded if one valve becomes defective. Further, the microvalves do not have standard fluidic and electrical connectors as do solenoid valves, allowing the rearrangement of the valves for different functions.
As stated above, while the microvalve inside the T08 can of ICS 4425 or the Fluistor.TM. valve is very small, the package is quite large and each package requires separate fluidic connections and electrical connections. It can be seen that in order to provide a plurality of valves, as in the Colleran '422 patent, would require a large number of fluidic lines and a large number of electrical connections, resulting in a very complex and confusing array of discrete elements, including valves, fluidic lines and connectors, and electrical lines and connectors.
What is needed is an electrofluidic module, specifically a highly miniaturized electrofluidic module which can perform the function of a multiplexing system able to selectively connect one or more of a plurality of fluidic inlets to one or more of a plurality of fluidic outlets, but which occupies a very small volume, uses very little electrical current to control and thus produces little waste heat and which is reliable and may be manufactured inexpensively. Preferably, such a module should permit easy installation and replacement and should be provided with a standard fluidic interface and a standard electronic interface.